The invention resides in a method for operating a compressor near the compressor pumping limit which includes a control arrangement for adjusting the momentary operating point of the compressor wherein at least one value of a variable parameter of the compressor is measured, compared with a desired value and, upon occurrence of an excessive deviation, the control arrangement is activated so as to reduce the deviation.
DE 43 16 202 A1 discloses a method for the surveillance of the pumping limit of a turbocharger. The operating range of compressors is limited for high mass flows and, at the same time, high loads by the pumping limit whereby the actually usable compressor performance field width is limited particularly with respect to the pumping limit, from which a minimum distance must be maintained in order to avoid an unacceptably high loading of the compressor wheel.
In order to prevent exceeding the pump limit into the unacceptable range, in accordance with DE 43 16 202 A1, a control arrangement is provided wherein the pressures and the volume flows through the compressor are measured, compared in a control unit with corresponding desirable values and, with an unacceptable deviation of the actual values from the desired values, a guide structure arranged upstream or downstream of the compressor wheel is so adjusted that a desirable distance from the pumping limit is maintained. In this connection, it is however a problem that the desired values which are employed for a comparison with the measured values must be determined in advance on the basis of a reference compressor which limits a dynamic adaptation to conditions changing during the operation, for example as a result of soiling, wear or heat influences or makes it even impossible.
It is the object of the present invention to make a utilization of the operating range of a compressor within the compressor characteristic performance field possible to the largest extent while avoiding transgression of the pumping limit.